Clutch gearing especially for a manual transmission

ABSTRACT

In a coupling tooth formation, in particular in a gear box, either on a gear sleeve or on a gear wheel, the teeth are fitted to the base end of a cylindrical base ( 12 ) in relation to the rotational axis, elongate in axial direction and provided at their coupling end with a roof outline sloping from the tooth base towards the tooth head, comprising a rounded roof edge ( 5 ); the radius of the roof edge rounding increases from the tooth base towards the tooth head according to a pre-set function in order to design the procedure of the tracking process after the initial contact as smoothly running as possible.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a coupling tooth formation, in particular in agear box, either on a gear sleeve or on a gear wheel, the teeth of whichare positioned at a cylindrical base in relation to the rotational axis,elongate in axial direction and provided at their coupling end with aroof contour sloping from the tooth base towards the tooth head,comprising a rounded roof edge.

2. Description of Related Art

Gear sleeves are known (DE 19604386 A1, DE 19531155 A1) the teeth ofwhich comprise roof-shaped surfaces which together form a rounded edge.Furthermore, symmetrical and asymmetrical roof configurations are knownand those having a sloping roof contour; the latter serves toadditionally facilitate tracking of the two teeth partners of a set ofcoupling teeth. In this context it is the object of the person skilledin the art to attain that during the initial contact of the two toothformations their contact is reduced to a minimum of points or lines;this permits the friction-reduced and, therefore, smooth-runninginterlocking of both tooth formation partners of a set of couplingteeth. However, in this process still too little attention is paid tothe further procedure of the tracking process, that is to say, after theinitial contact has already taken place. This is where the presentinvention sets in by pursuing the object of realizing the smoothestpossible transition in the phase between the initial contact and thefinal coupling position.

SUMMARY OF THE INVENTION

This object is attained according to the invention in that the radius ofthe roof edge rounding increases from the tooth base towards the toothhead according to a pre-set function.

This measure results in a continuous increase of the contact points orthe extension of the contact lines until finally the desired surfacecontact is attained between the power transmitting tooth flanges. Duringthe initial contact, i.e. in the proximity of the foot region with acorrespondingly greater tooth depth, the tooth formation offers aparticularly great tolerance for the mutual engagement as the radius ofthe roof edge rounding is relatively small there. With an increasingengagement, i.e. increasing axial shifting of the two interlockingteeth, an increasing centering of the two teeth formations in relationto one another is brought about according to the widening of the roofedge in the tooth head region due to the relatively larger radii thereof the roof edge rounding, until their maximum contact is realized uponreaching complete engagement.

In the process, the person operating the gear box, gets the impressionof a smoother gear changing procedure as if, after the initial contact,the switched gear is put in quasi automatically. This impression isfurther strengthened if the increase in radius proceeds progressively,e.g. according to an exponential function or a circular function insteadof a linear function.

A particularly advantageous progression from the foot cylinder towardsthe head cylinder of the tooth formation defines an altogether six-foldincrease of the radius in which context doubling is only reached atabout 60% of the relative tooth height.

As regards the configuration of a short tooth formation of this kind asa whole, one could, in a graphic transposition of the rules according tothe invention, compare the roof shape, in the case of a symmetricaltooth, with a human nose which, at the base of the nose, correspondingcomparatively to the foot cylinder of the tooth formation, is designedparticularly narrow, subsequently becoming broader up to the tip of thenose. The bridge of the nose may in this context slope eitherrectilinearly or by being bent downwardly, the lowest point of the nose,by way of comparison, corresponding to the head cylinder of the toothformation. In order to remain with the demonstrated image, thelongitudinal body axis of the nose carrier would correspond to therotational axis of the tooth formation.

As regards the oblique roof surfaces laterally adjoining the roof edge,these are preferably designed as level planes. This facilitates theirshaping in a deformation process. e.g. for the manufacture as a forgedpart, in which context one or more calibrating steps may follow onto aforging step.

Arched roof surfaces are, however, likewise conceivable within the scopeof the invention, but their precise manufacture encounters difficultieswith regard to minimum deformations as in the case of coupling teeth.This applies similarly to asymmetrical roof shapes, the manufacture ofwhich presupposes likewise a high precision of the forming tools or ofthe deformation process.

BRIEF DESCRIPTION OF THE DRAWING

The invention is elucidated in the following by way of a number ofembodiments. There are shown in

FIGS. 1 to 4 a tooth of a tooth formation with a proportional radiusincrease, in four different views.

FIG. 5 a graphic illustration of the proportional radius increase,

FIG. 6 patterns of the radius increase in a graphic illustration,

FIG. 7 a graphic illustration of the progressive radius increase,

FIGS. 8 to 11 a tooth having a symmetrical roof shape and a progressiveradius increase, in four different views,

FIGS. 12 to 15 a tooth having an asymmetrical roof shape and aprogressive radius increase, in four different views,

FIG. 16 a tooth having a symmetrical roof shape in a perspective viewand

FIG. 17 a tooth having an asymmetrical roof shape in a perspective view

DETAILED DESCRIPTION OF THE INVENTION

The tooth illustrated in FIGS. 1 to 4 of a tooth formation, e.g. in asliding sleeve, is designed, as is apparent from the plan view (FIG. 3),somewhat trapezoidal in cross-section, i.e. from the tooth base 1 to thetooth head 2 it comprises obliquely converging side flanges 3. The roofoutline of its symmetrical roof shape 4 is characterized by a roof edge5 sloping from the tooth base 1 to the tooth head 2, being rounded asillustrated in the side elevation according to FIG. 2 as well as in theperspective view according to FIG. 4. Level roof surfaces 6 follow ontothe rounded roof edge 5 on both sides. In accordance with the divergingcourse towards the tooth head 2 of the lateral cutting lines 7 of therounded roof edge with the adjoining roof surfaces 6, it is readilyapparent that the radius of the rounded roof edge increases from thetooth base 1 towards the tooth head 2. This, in the case of level roofsurfaces 6, results in a deviation of the roof edge 5 from thetheoretical cutting edge 8 of the two roof surfaces 6 illustrated inFIG. 1. Arrow P1 denotes the sliding direction of the tooth duringcoupling with the counter tooth formation.

In the plan view according to FIG. 3 the tooth base is illustrated in aslightly curved manner. This pattern is to illustrate the base of thecoupling teeth which continues with a dash-dotted extension line 9 thesaid base being a cylindrical surface having a longitudinal axisparallel to the sliding direction according to arrow P1.

FIG. 5 is a graphic elucidation of the roof edge rounding of a tooth ofa coupling tooth formation according to FIGS. 1 to 4. The roof edge 5 ina sloping manner follows onto the base, indicated by a first structuralline 10. Between a radius R1 in the region of the tooth base and aradius R2 in the region of the tooth head four additional radii R_(i)are indicated which in their relationship to one another suggest alinear increase of the roof edge radius from the tooth base towards thetooth head.

According to FIG. 6 the radius increase (y-axis) is graphicallyillustrated by way of example in the roof edge region in relation to therelative tooth height (x-axis), the tooth height being measured in thedirection of a second structural line 11 (FIG. 5), increasing from thetooth base towards the tooth head. Two modifications are indicated inFIG. 6, namely one, straight line I suggesting a linear course of theradius increase, as realized, for example, in a roof shape according toFIGS. 1 to 4; furthermore a curve II of a progressive course of theradius increase as realized, for example, in a symmetrical roof shapeaccording to FIGS. 8 to 11 or in an asymmetrical roof shape according toFIGS. 12 to 15. For both roof shapes reference numerals corresponding toFIGS. 1 to 4 were used so that the renewed elucidation in detail of theindividual components of these tooth designs may be dispensed with.

In the case of the tooth design having a progressive radius increaseaccording to FIGS. 8 to 11, the roof edge 5 extends opposite thetheoretical cutting edge 8 of the level roof surfaces 6 following aprogressively sloping curve which corresponds to the outline of the roofedge 5 according to FIG. 7.

In an asymmetrical tooth design according to FIGS. 12 to 15 the roof ispulled to one side in such an extreme manner that on the steep side ofthe roof the roof surface coincides with the side flange 3, as isapparent particularly clearly from FIG. 13.

In the drawing all edge lines between the roof surfaces 6, the sideflanges 3 and the head surface 2 are drawn by double lines. This servesto indicate the formation of small radii.

FIGS. 16 and 17 each illustrate in a diagram, supplemented by a linepattern, a section of a tooth having a symmetrical tooth shape (FIG. 16)as well as of a tooth having an asymmetrical tooth shape (FIG. 17). Theteeth are fitted to a cylindrical basic body having a base 12 and, withthe highest point of their roof surface each follow on to a coversurface 13 of the basic body in a flush manner. The rounded radii areclearly apparent both in the region of the roof edge 5 and also betweenthe roof surfaces 6 and the side flanges 3.

Coupling teeth exist where the base of the teeth opposite the roofsurface is also forming part of the basic body by providing anappropriate shoulder 14 there, indicated in FIG. 17 by dashed lines.

What is claimed is:
 1. A gear coupling tooth for arrangement on a gearhaving a rotational axis and a cylindrical outer surface, said toothcomprising: a tooth base adapted for extension along the gearcylindrical outer surface, a tooth head, and a rounded roof edge slopingfrom the tooth base towards the tooth head, said rounded roof edgefarther comprising a radius that increases from the tooth base towardsthe tooth head.
 2. A gear coupling tooth according to claim 1, whereinthe radius of the rounded roof edge increases linearly from the toothbase to the tooth head.
 3. A gear coupling tooth according to claim 1,wherein the radius of the rounded roof edge increases progressively fromthe tooth base to the tooth head.
 4. A gear coupling tooth according toclaim 1, further comprising sloping roof surfaces abutting the roundedroof edge.
 5. A gear coupling tooth according to claim 1, wherein therounded roof edge slopes progressively from the tooth base to the toothhead.
 6. A gear coupling tooth according to claim 1, wherein the roundedroof edge slopes asymmetrically from the tooth base to the tooth head.